1. Field of the Invention
The present invention relates to a tape end detection mechanism for a tape cassette suitable for use with a tape recorder such as a video cassette recorded (VCR).
2. Description of the Related Art
An example of a tape end detection mechanism for a tape cassette will be described with reference to FIGS. 1 and 2.
As shown in FIGS. 1 and 2, there is provided a tape cassette 1 having a tape supply reel 2 and a tape takeup reel 3 therein. A tape T supplied from the tape supply reel 2 is guided across a mouth portion 5 by a tape guide 4 disposed at the tape supply reel 2 side and a tape guide 6 disposed at the tape takeup reel 3 side, and the tape is then wound around the takeup reel 3.
A tape detection hole 7 is bored in the cassette 1 adjacent the mouth portion 5 intermediate the supply reel 2 and the takeup reel 3. Light-emitting elements 8 and 9 each formed by a light-emitting diode (LED) are disposed on the mechanical deck so as to extend into the tape detection hole 7. Light beams 10, 11 emitted in the left and right directions from the light-emitting elements 8 and 9 are received by light-emitting receiving elements 12, 13 provided on the mechanical deck at opposite sides, respectively, of the cassette 1. The tape T between the tape supply reel 2 and the tape guide 4 crosses the light beam 10. Also, the tape T between the tape guide 6 and the tape takeup reel 3 crosses the other light beam 11.
The tape T is composed of a recording portion which is substantially opaque or has a low light transmittance and leader portions which are substantially transparent or have a high light transmittance provided at respective ends of the recording portion. Owing to a difference of light transmittance between the recording portion and the leader portions, it is possible to detect respective ends (starting end and ending end) of the tape T by optically detecting a difference in the intensity of light introduced into the light-receiving elements 12, 13. The heights of the paths of the light beams 10, 11 which are introduced into the light-receiving elements 12, 13 from the light-emitting elements 8, 9, shall be determined according to the format of the tape cassette.
The light-emitting elements 8, 9 are electrically connected to a flexible base 16 through conductors 14 and 15, respectively, as shown in FIG. 3 in an enlarged scale. The light-emitting elements 8, 9 are supported by supporting members 18, 19 which project from a metal chassis 17 on the mechanical deck. The flexible base 16 is U-shaped in cross-section and acts as a spacer so as to prevent the conductors 14, 15 and the supporting members 18, 19 from contacting one another.
The same Assignee of the present application has the following patents and patent applications, i.e., U.S. Pat. Nos. 4,989,111, 5,024,394.
While the heights of the light paths of the light beam 10, and 11 received by the light-emitting elements 12, 13 from the light-emitting elements 8, 9 are determined according to the tape cassette format, when the tape cassette is reduced in thickness so that the position of the tape detection hole 7 is lowered, the heights of the light-emitting elements 8, 9, i.e., the heights of the light paths of the light beams 10, 11 are reduced inevitably. As a consequence, the flexible base 16 and the conductors 14, 15 have to project from the lower surface of the tape cassette 1 by a distance corresponding to the decrease in the heights of the light paths. In other words, the portions of base 16 and conductor 14, 15 that project from the lower surface of the tape cassette 1 need to be accommodated within the mechanical deck so that the peripheral mechanisms disposed within the mechanical deck have to be disposed so as not to disturb the tape cassette 1. As a result, the mechanical deck either becomes thick or the mechanisms of the mechanical deck are restricted considerably from a design standpoint.
Furthermore, if the tape detection hole is made smaller, then the tape cassette cannot be loaded on the mechanical deck with a sufficient positional freedom.